1. Field of the Invention
The present invention relates to a connection part for optical fibers for optical communication, particularly to an optical fiber connector part comprising a ferrule having excellent shape stability. The present invention relates also to granular zirconia-alumina having excellent sintering characteristics.
2. Description of the Related Art
The connector employed for optical fiber connection in the optical fiber communication system is constituted of plugs 2 and an adapter 1 as shown in FIG. 1. The plug 2 holds a ferrule of a precise cylinder outside diameter having a finely machined capillary hole 31 in the center. An optical fiber is inserted into the hole and is integrated with the ferrule. The tip of the ferrule is worked to have a spherical convex face. A pair of the plugs are forced into the adapter 1 from the both sides of the adapter for fiber connection. If the axes of the optical fibers deviate from each other, optical loss occurs to cause signal transmission loss. Therefore the ferrule part used should have a precisely controlled shape in the outside diameter, the inside diameter, the length, and so forth. The adapter 1 has a sleeve 4 as shown in FIG. 3 to hold and align the two ferrules 3 elastically. Conventionally, a sintered zirconia compact partially stabilized by yttria is used as the material for forming the ferrule and the sleeve part. This sintered zirconia compact, which has a small crystal particle size, high strength, and high toughness, can be worked precisely at the surface and is less liable to develop defects such as chipping, being suitable for the material for ferrules, sleeves, and the like parts. However, the ferrule formed from the sintered zirconia compact is liable to be deformed at the spherical tip face during long-term press connection, giving failure in re-connection of the fiber disadvantageously. Therefore, ferrule or sleeve parts are demanded which are stable dimensionally to retain the spherical shape of the tip face on connection-disconnection of the connector.
An optical fiber connector is known in which a pair of inner rings having an optical fiber fitted in the capillary hole thereof are inserted into a sleeve from both ends of the sleeve to bring the tips of the inner rings into contact, the inner rings and the sleeve being formed from zirconia ceramics (JP-A-5-333239).
The above optical fiber connector part is obtained by molding a powdery zirconia material containing a stabilizer such as Y.sub.2 O.sub.3, MgO, and CaO into a prescribed shape and then sintering the molded article at a temperature ranging from 1400.degree. C. to 1600.degree. C. The optical fiber connector part made from this sintered zirconia compact can be deformed at the spherical face of the ferrule tip by the press contact as mentioned above, thereby resulting in contact failure at re-connection after disconnection, and is not suitable for the optical fiber connector part.
The inventors of the present invention noticed the crystalline particle diameter and the chemical constitution of the sintered compacts of zirconia-alumina composite oxide, and studied comprehensively the workability of the surface of the optical fiber connector part and the shape stability of the spherical tip face of the ferrule formed from the compact to complete the present invention.
The inventors of the present invention noticed also the average particle diameter and the granule properties of a mixture of particulate zirconia containing a solid-solute stabilizer and particulate alumina for raw material of production of a sintered compact of the above zirconia-alumina composite oxide, and studied comprehensively the sintering characteristics of the particle mixture to complete the present invention.